Many modern smartphones and mobile devices can determine their own location using the Global Positioning System (GPS). In a typical implementation, the smartphone receives signals from multiple GPS satellites. The GPS signals help indicate a distance between the smartphone and the satellites. The smartphone then uses the GPS signals to determine its location, which is typically represented as a geo coordinate or GPS coordinate (e.g., a pair of latitude and longitude coordinates.) An advantage of the GPS coordinate system is that it is widely adopted and compatible with a broad array of location-aware applications.
One disadvantage of the GPS system, however, is that it is ineffective or substantially less effective in indoor environments, because the walls and ceilings of a building may block the satellite signals. Thus, there have been various efforts to develop an indoor GPS system.